1. Field of the Invention
The present invention is related to a driving circuit, and particularly to a driving circuit that utilizes a switch, a detecting unit, and an energy storage unit to enhance energy conversion efficiency.
2. Description of the Prior Art
Please refer to FIG. 1A. FIG. 1A is a diagram illustrating a driving circuit 100 for driving light emitting diodes according to the prior art. As shown in FIG. 1A, the driving circuit 100 includes a rectifier 102 and a current supply unit 104. The rectifier 102 is used for receiving an alternating current voltage AC, and generating a first voltage V1 according to the alternating current voltage AC. The first voltage V1 is a direct current voltage and varies periodically with time. The first voltage V1 is used for driving a series of light emitting diodes 106, and the series of light emitting diodes 106 includes at least one light emitting diode. As shown in FIG. 1A, input power of the driving circuit 100 is a sum of power consumption PLED of the series of light emitting diodes 106 and power consumption PLOSS of the current supply unit 104. In addition, energy conversion efficiency ECE of the driving circuit 100 is generated by equation (1):ECE=PLED/PLOSS  (1)
Please refer to FIG. 1B. FIG. 1B is a diagram illustrating a relationship between the power consumption PLED of the series of light emitting diodes 106 and the first voltage V1. As shown in FIG. 1A and FIG. 1B, after the series of light emitting diodes 106 is turned on, the power consumption PLOSS of the current supply unit 104 is increased with increase of the first voltage V1. However, the power consumption PLED of the series of light emitting diodes 106 is not increased with the increase of the first voltage V1 because the power consumption PLED is generated by equation (2):PLED=VLED×Id  (2)
As shown in equation (2), VLED is a voltage drop of the series of light emitting diodes 106, and Id is a driving current of the series of light emitting diodes 106. Therefore, the driving circuit 100 shown in FIG. 1A is not a good choice for driving light emitting diodes.